The food industry is attempting to produce foods that are both high quality and have reduced fat and/or reduced calories. A prime target category is the entire family of fried foods, and particularly deep-fat french-fried potatoes.
French-fried potatoes, for example, are generally prepared from sliced raw potatoes that have been subjected to heat pretreatment, followed by a direct contact deep fat frying process at high temperature. Depending upon the exact nature of the pretreatments, a significant quantity of oil is taken up by the potato during the frying process.
Certain technologies have appeared in practice promising oil reduction, but do not provide acceptable levels of quality in the finished product. Among these are spraying partially fried potatoes with high melting triglyceride solids for oven baking as an imitation for deep-fat frying. This method produces fries having a quality texturally and hedonically different from their deep-fat fried analogues. Variations in drying conditions just prior to the par frying step allow for reduced oil fries, but with the penalty of poor eating quality and a chewier or harder texture. This is a result of the significantly lower moisture content caused by over drying the fried potato strips.
In U.S. Pat. No. 5,906,483, Kloos describes a process in which the potatoes are formed into slices, in the form of either potato chips or french fries, and subjected to hot water treatment for the removal of starch and the generation of color. Following this set of operations, the potatoes are placed on a nonstick cookie sheet and baked to a predetermined color end point.
In U.S. Pat. No. 4,542,030, Haury and Hensley describe a process in which potato slices are dipped in a solution containing sodium acid pyrophosphate (SAPP) and caramel and/or glucose. Following the dipping and blanching operations, the potato strips are subjected to a brief air drying step and then either to deep-fat frying or hot oil spraying. Part of the oil reduction is claimed to result from a combination of high temperature and short cooking time or low temperature and extended cooking time. Freezing follows the par-frying step. The potatoes are finished by a baking process.
In U.S. Pat. No. 3,865,964 Kellermeier et al. describe a process in which potatoes are washed, peeled, sliced and blanched followed by conventional par-frying in hot oil, and freezing. Following freezing, the fried potatoes are spraying with a controlled amount of frying fat in globule form, which solidifies on contact with the cold surface. For final consumption, the fries are thawed and baked.
In U.S. Pat. No. 4,917,908, Prosise describes a process in which potatoes are coated with polyvinyl pyrrolidone, acting as an oil barrier. In the described process, the potatoes are sliced, washed and dipped into either water or a solution of polyvinylpyrrolidone for 10 minutes. Following this, the potatoes are deep fried. An oil reduction figure of 28% is given, but the neither the described process nor the control process reflect the state of the art in the retail food industry, which often involves multiple blanching steps and both a par- and finish frying step.
In U.S. Pat. No. 3,846,572, Nonaka et al. describe a process in which reduced fat french fries are prepared. Raw potato slices are frozen in dichlorodifluoromethane, leached in water, fried and subsequently washed again in oil-free dichlorodifluoromethane. Both the Nonaka and the Prosise methods are associated with non-natural chemical additives, which are not acceptable to either consumers at large or the retail food industry.
A process for producing low-fat potato chips is discussed in U.S. Pat. No. 4,283,425. Birney and Yuan. Specifically aimed at potato chips, their process involves coating a raw sliced potato with a globular protein, adding a layer of oil over the protein and subjecting the slice to microwave heating.
Proteins have been used as oil barrier coatings in some applications. Solutions of prolamines for example have been used in food systems, such as candy coatings. Use of prolamine coatings is described by James in U.S. Pat. No. 2,377,237; by Cosler in U.S. Pat. No. 2,791,509; and by Anker et al. in U.S. Pat. No. 3,653,925. All previous applications utilizing prolamines, however, have been made from non-aqueous solvents, such as ethanol.
None of the available methods results in a product having acceptable sensory quality and a significantly reduced fat content.